Mutation frequency of plasmid DNA and Escherichia coli following long-term space flight on Mir

Combined Environment Simulator for Low-Dose-Rate Radiation and Partial Gravity of Moon and Mars

Deep space exploration by humans has become more realistic, with planned returns to the Moon, travel to Mars, and beyond. Space radiation with a low dose rate would be a constant risk for space travelers. The combined effects of space radiation and partial gravity such as on the Moon and Mars are unknown. The difficulty for such research is that there are no good simulating systems on the ground to investigate these combined effects. To address this knowledge gap, we developed the Simulator of the environments on the Moon and Mars with Neutron irradiation and Gravity change (SwiNG) for in vitro experiments using disposable closed cell culture chambers. The device simulates partial gravity using a centrifuge in a three-dimensional clinostat. Six samples are exposed at once to neutrons at a low dose rate (1 mGy/day) using Californium-252 in the center of the centrifuge. The system is compact including two SwiNG devices in the incubator, one with and one without radiation source, with a cooling function. This simulator is highly convenient for ground-based biological experiments because of limited access to spaceflight experiments. SwiNG can contribute significantly to research on the combined effects of space radiation and partial gravity.

Characterization of Aspergillus fumigatus Isolates from Air and Surfaces of the International Space Station

One mission of the Microbial Observatory Experiments on the International Space Station (ISS) is to examine the traits and diversity of fungal isolates to gain a better understanding of how fungi may adapt to microgravity environments and how this may affect interactions with humans in a closed habitat. Here, we report an initial characterization of two isolates, ISSFT-021 and IF1SW-F4, of Aspergillus fumigatus collected from the ISS and a comparison to the experimentally established clinical isolates Af293 and CEA10. Whole-genome sequencing of ISSFT-021 and IF1SW-F4 showed 54,960 and 52,129 single nucleotide polymorphisms, respectively, compared to Af293, which is consistent with observed genetic heterogeneity among sequenced A. fumigatus isolates from diverse clinical and environmental sources. Assessment of in vitro growth characteristics, secondary metabolite production, and susceptibility to chemical stresses revealed no outstanding differences between ISS and clinical strains that would suggest special adaptation to life aboard the ISS. Virulence assessment in a neutrophil-deficient larval zebrafish model of invasive aspergillosis revealed that both ISSFT-021 and IF1SW-F4 were significantly more lethal than Af293 and CEA10. Taken together, these genomic, in vitro, and in vivo analyses of two A. fumigatus strains isolated from the ISS provide a benchmark for future investigations of these strains and for continuing research on specific microbial isolates from manned space environments. IMPORTANCE As durations of manned space missions increase, it is imperative to understand the long-term consequence of microbial exposure on human health in a closed human habitat. To date, studies aimed at bacterial and fungal contamination of space vessels have highlighted species compositions biased toward hardy, persistent organisms capable of withstanding harsh conditions. In the current study, we assessed traits of two independent Aspergillus fumigatus strains isolated from the International Space Station. Ubiquitously found in terrestrial soil and atmospheric environments, A. fumigatus is a significant opportunistic fungal threat to human health, particularly among the immunocompromised. Using two well-known clinical isolates of A. fumigatus as comparators, we found that both ISS isolates exhibited normal in vitro growth and chemical stress tolerance yet caused higher lethality in a vertebrate model of invasive disease. These findings substantiate the need for additional studies of physical traits and biological activities of microbes adapted to microgravity and other extreme extraterrestrial conditions.

CPD photolyase gene from Spinacia oleracea: repair of UV-damaged DNA and expression in plant organs

The UV-B radiation contained in solar radiation has deleterious effects on plant growth, development and physiology. Specific damage to DNA caused by UV radiation involves the cyclobutyl pyrimidine dimers (CPD) and the pyrimidine (6-4) pyrimidone photoproducts. CPDs are repaired by CPD photolyase via a UV-A/blue light-dependent mechanism. The gene for the class II CPD photolyase has been cloned from higher plants such as Arabidopsis, cucumbers and rice. We isolated and characterized the cDNA and a genomic clone encoding the spinach class II CPD photolyase. The gene consisted of 3777 bases and 9 exons. The sequence of amino acids predicted from the nucleotide sequence of the cDNA of the gene was highly homologous to that of the higher plants listed above. When a photolyase-deficient Escherichia coli strain was transformed with the cDNA, photoreactivation activity was partially restored, by the illumination with photoreactivating light, resulting in an increased survival and decreased content of CPDs in the Escherichia coli genome. In both the male and female plants, the gene was highly expressed in leaves and flowers under the condition of 14-h light and 10-h dark cycle. The expression in the roots was quite low compared with the other organs.